Paper 2- Mole calculations
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How do you work out the relative formula mass (Mr) from the relative atomic mass (Ar) e.g. MgCl2
Ar of Mg= 24 Ar of Cl= 35.5 24 + (35.5x2) = 95 Mr- MgCl2= 95
what is the formula to work out mass, moles and mr
mass mol x mr
How do you work out the empirical formula
1) list all elements in the compound 2) underneath them write experimental masses 3) find number of moles of each element by dividing each mass by Ar 4) divide by smallest 5) multiply to get whole numbers
molecular formula steps
mr empirical mass empirical formula x answer
solutions and concentrations formula
mol vol x conc
water of crystallisation steps CaCl2.xH20
1) list the salt and water 2) write experimental masses 3) divide by mr 4) divide by smallest
reacting masses calculation steps e.g. find mass of iron produced when 44.8g of iron oxide is reduced by carbon monoxide: Fe2O3 + 3CO –> 3CO2 + 2Fe
1) find data 2) convert to moles 3) use ratios from equation 4) answer ques using appropriate moles equation
gas volumes formula
volume moles x 24000
gas volumes calculation steps
1) find moles 2) use ratios from equation 3) answer ques using appropriate moles equation
titration calculation formula
mol vol x conc
titration calculation steps
1) work out the moles 2) use ratios 3) work out concentration/ volume
percentage yield equation
actual yield/ theoretical yield x 100